When 1 dm³$1 \, dm^{3}$ of CO₂$CO_{2}$ gas is passed over hot coke the volume of gaseous mixture after complete reaction at STP becomes 1.4 dm³$1.4 \, dm^{3}$. The composition of the gaseous mixture at STP is:

Related Formula

Core Logic

Structure of Urea: NH₂-CO-NH₂$NH_2-CO-NH_2$ (Molecular formula: CH₄N₂O$CH_4N_2O$). Each molecule of urea contains 4 hydrogen atoms. Given mass of urea = 5.4 g$5.4 \text{ g}$. Molar mass of urea = 60 g/mol$60 \text{ g/mol}$.

Moles of urea = (5.4)/(60) = 0.09 mol$= \frac{5.4}{60} = 0.09 \text{ mol}$.

Step 1: Calculate Total Hydrogen Atoms

Number of hydrogen atoms = Moles of urea × 4 × NA$= \text{Moles of urea} \times 4 \times N_A$ Number of hydrogen atoms = 0.09 × 4 × (6.022 × 10²³)$= 0.09 \times 4 \times (6.022 \times 10^{23})$ Number of hydrogen atoms = 0.36 × 6.022 × 10²³$= 0.36 \times 6.022 \times 10^{23}$ Number of hydrogen atoms = 2.16792 × 10²³ ≈ 2.168 × 10²³$= 2.16792 \times 10^{23} \approx 2.168 \times 10^{23}$

Pattern Recognition

Don't forget to multiply the total moles of the molecule by the specific atom count (atomicity) requested. Urea has 4 hydrogens per molecule.

Chapter Mix

Class 11 Chemistry: Some Basic Concepts of Chemistry